1. Field of the Invention
The invention relates to the remote exchange of information between a station and one or more portable objects.
It applies particularly but not exclusively to the exchange of information between an electronic memory card, for example a "chip card", and a terminal.
2. Description of the Related Art
The concept of "remote" exchange is contrasted here with that of an exchange requiring a contact interface, of electrical or some other kind, between the card and the terminal, as is for example the case in telecard pay-phones.
This type of interface can be regarded as fairly constraining in a certain number of applications such as identification of people or control of access by people to a building. It can be equally constraining in the case of banking transactions requiring the card to be passed into a slot of the terminal.
A device for remote exchange of data between a portable object and a station has been described in European Patent Application No. 89 403398.3 of Dec. 7, 1989.
In this prior device, there is provided, in the station, a station-dialogue unit able to define a range of action, and, in the portable object, an object-dialogue unit possessing an active state in which it is able to mutually interact remotely with the station-dialogue unit inside the range of action, in order to effect the exchange of information.
Although this prior device teaches a way of producing in hardware such a data exchange between the station and a single portable object, it is expedient to solve the problems which arise when several carriers equipped respectively with several chip cards, for example, simultaneously are present in the range of action of the station.
No device is currently known permitting simple and efficient solution of the potential conflicts which can result from this multiple presence of portable objects before the station.
The invention aims to solve this problem.